CO_2对X70钢在近中性pH值溶液中硫酸盐还原菌腐蚀行为的影响

Effects of CO_2 on SRB Influenced Corrosion Behavior of X70 Steel in Near-neutral pH Solution

对不同CO_2浓度下硫酸盐还原菌(SRB)在近中性pH值(NS4)溶液的生长曲线,以及SRB生长周期对溶液pH值和电导率的影响进行了研究。采用极化曲线、电化学阻抗技术和扫描电镜(SEM)研究了CO_2浓度对X70钢在有菌的NS4溶液中的腐蚀行为。结果表明:CO_2在SRB代谢过程中起到了迟效碳源的作用,使SRB繁殖出现二次生长。SRB新陈代谢消耗了有机碳并释放出无机离子使溶液电导率在SRB对数生长期增加。SRB二次生长期消耗无机碳源(CO_2)和化合物时并不产生新的离子导致溶液电导率下降。SRB生长周期对溶液pH值没有影响,pH值随时间和CO_2浓度增加而略有增加。X70钢在有菌溶液中表面膜层表现出圈状裂纹,随CO_2浓度增加,X70钢在NS4菌液中表面膜层致密性变差。CO_2促进了金属表面点蚀的发展。

The growth curve of sulfate reducing bacterial（SRB） in the near-neutral pH solution（NS4）, and the effect of SRB growth cycle on the pH value and the conductivity of the solution were investigated. Then the corrosion behavior of X70 steel in CO2 containing NS4 solutions with SRB was studied by means of electrochemical impedance spectroscopy（EIS） and electro scanning microscope（SEM）.The results showed that CO2 played a role as a slowly available carbon source to maintain the growth and metabolism process of SRB, which resulted in a secondary growth phase of SRB. The organic carbon was consumed by SRB metabolism, and thereby the inorganic ions were released at the same time,which resulted in the increase of solution conductivity in the logarithmic phase of SRB growth. CO2 was consumed as the inorganic carbon source in the secondary growth phase,while the inorganic ions were not emerged in the case, so the solution conductivity decreased. The growth cycle had little influence on p H value of the solution, which increased slightly with the increasing CO2 concentration and time. There were circle-shaped cracks on the X70 steel surface in the bacterial solution. With the increasing CO2 concentration in the bacterial solution, the compactness of the oxide scales formed on X70 steel surface gradually became worse, while pitting corrosion on the steel was promoted.